#!/usr/bin/env python3
#
# Copyright 2021 Graviti. Licensed under MIT License.
#

"""The implementation of the TensorBay repr."""

from abc import ABC
from enum import Enum, auto
from typing import Any, Callable, Dict, Iterable, Mapping, Sequence, Tuple, Type, TypeVar, Union


class ReprType(Enum):
    """ReprType is an enumeration type.

    It defines the repr strategy type and includes 'INSTANCE', 'SEQUENCE' and 'MAPPING'.

    """

    INSTANCE = auto()
    SEQUENCE = auto()
    MAPPING = auto()


class ReprMixin:
    """ReprMixin provides customized repr config and method."""

    _repr_type = ReprType.INSTANCE
    _repr_attrs: Iterable[str] = ()
    _repr_maxlevel = 1
    _repr_non_empty = False

    def __repr__(self) -> str:
        return _repr1(self, self._repr_maxlevel, self._repr_maxlevel, True)

    def __str__(self) -> str:
        return _repr1(self, self._repr_maxlevel, self._repr_maxlevel, False)

    def _repr_head(self) -> str:
        return self.__class__.__name__


class _ReprConfig:
    """Config for customized repr method.

    Arguments:
        indent: The indent width for different level repr string.
        maxlist: The max items displayed in the sequence repr string.
        maxdict: The max items displayed in the mapping repr string.

    """

    def __init__(self, indent: int = 2, maxlist: int = 16, maxdict: int = 16) -> None:
        self.indent = indent
        self.maxlist = maxlist
        self.maxdict = maxdict

    @property
    def indent(self) -> int:
        """The getter of repr indent width.

        Returns:
            The indent width of repr config.

        """
        return self._indent

    @indent.setter
    def indent(self, indent: int) -> None:
        """The setter of repr indent width.

        Arguments:
            indent: The width of the ident to be set.

        """
        self._indent = indent
        self._indent_str = " " * indent


repr_config = _ReprConfig()


# Explicitly inherit from 'abc.ABC' to tell pylint it is a abstract class
# Reference:
# - https://github.com/PyCQA/pylint/issues/3098
# - https://github.com/PyCQA/pylint/pull/3446
class _ReprSequence(ReprMixin, Sequence[Any], ABC):
    ...


class _ReprMapping(ReprMixin, Mapping[Any, Any], ABC):
    ...


_ReprPrinter = Callable[[Any, int, int, bool], str]

_PRINTERS: Dict[Union[Type[Any], ReprType], _ReprPrinter] = {}


class _PrinterRegister:
    """Decorator class to register repr printer functions to '_PRINTERS'.

    Arguments:
        key: The key of the '_PRINTERS' for repr dispatch.

    """

    _S = TypeVar("_S", bound=_ReprPrinter)

    def __init__(self, key: Union[Type[Any], ReprType]) -> None:
        self._key = key

    def __call__(self, printer: _S) -> _S:
        _PRINTERS[self._key] = printer
        return printer


def _repr1(obj: Any, level: int, maxlevel: int, folding: bool) -> str:
    """Customized repr method.

    Arguments:
        obj: The object need to be transferred to repr string.
        level: The current repr level.
        maxlevel: The max repr level.
        folding: Whether fold the "repr" of the object.

    Returns:
        "repr" of the object.

    """
    # pylint: disable=protected-access
    printer_key = obj._repr_type if hasattr(obj, "_repr_type") else type(obj)
    printer = _PRINTERS.get(printer_key, None)
    return printer(obj, level, maxlevel, folding) if printer else repr(obj)


@_PrinterRegister(ReprType.INSTANCE)
def _repr_instance(obj: ReprMixin, level: int, maxlevel: int, folding: bool) -> str:
    """Customized repr method for `ReprType.INSTANCE`.

    Arguments:
        obj: The object need to be transferred to repr string.
        level: The current repr level.
        maxlevel: The max repr level.
        folding: Whether fold the "repr" of the object.

    Returns:
        "repr" of the object.

    """
    # pylint: disable=protected-access
    return f"{obj._repr_head()}{_repr_attrs(obj, level, maxlevel, folding)}"


@_PrinterRegister(ReprType.SEQUENCE)
def _repr_sequence(obj: _ReprSequence, level: int, maxlevel: int, folding: bool) -> str:
    """Customized repr method for `ReprType.SEQUENCE`.

    Arguments:
        obj: The object need to be transferred to repr string.
        level: The current repr level.
        maxlevel: The max repr level.
        folding: Whether fold the "repr" of the object.

    Returns:
        "repr" of the object.

    """
    # pylint: disable=protected-access
    return (
        f"{obj._repr_head()} {_repr_builtin_list(obj, level, maxlevel, folding)}"
        f"{_repr_attrs(obj, level, maxlevel, folding)}"
    )


@_PrinterRegister(ReprType.MAPPING)
def _repr_mapping(obj: _ReprMapping, level: int, maxlevel: int, folding: bool) -> str:
    """Customized repr method for `ReprType.MAPPING`.

    Arguments:
        obj: The object need to be transferred to repr string.
        level: The current repr level.
        maxlevel: The max repr level.
        folding: Whether fold the "repr" of the object.

    Returns:
        "repr" of the object.

    """
    # pylint: disable=protected-access
    return (
        f"{obj._repr_head()} {_repr_builtin_dict(obj, level, maxlevel, folding)}"
        f"{_repr_attrs(obj, level, maxlevel, folding)}"
    )


@_PrinterRegister(list)
def _repr_builtin_list(obj: Sequence[Any], level: int, maxlevel: int, folding: bool) -> str:
    """Customized repr method for buildin type list.

    Arguments:
        obj: The object need to be transferred to repr string.
        level: The current repr level.
        maxlevel: The max repr level.
        folding: Whether fold the "repr" of the object.

    Returns:
        "repr" of the object.

    """
    return _repr_builtin_sequence(obj, level, maxlevel, folding, "[", "]")


@_PrinterRegister(tuple)
def _repr_builtin_tuple(obj: Sequence[Any], level: int, maxlevel: int, folding: bool) -> str:
    """Customized repr method for buildin type tuple.

    Arguments:
        obj: The object need to be transferred to repr string.
        level: The current repr level.
        maxlevel: The max repr level.
        folding: Whether fold the "repr" of the object.

    Returns:
        "repr" of the object.

    """
    return _repr_builtin_sequence(obj, level, maxlevel, folding, "(", ")")


@_PrinterRegister(dict)
def _repr_builtin_dict(obj: Mapping[Any, Any], level: int, maxlevel: int, folding: bool) -> str:
    """Customized repr method for buildin type dict.

    Arguments:
        obj: The object need to be transferred to repr string.
        level: The current repr level.
        maxlevel: The max repr level.
        folding: Whether fold the "repr" of the object.

    Returns:
        "repr" of the object.

    """
    if getattr(obj, "_repr_non_empty", False) and level <= 0:
        return "{...}"

    object_length = len(obj)
    if object_length == 0:
        return "{}"
    if level <= 0:
        return "{...}"
    newlevel = level - 1

    keys = tuple(obj)

    fold, unfold = _calculate_fold_number(object_length, repr_config.maxdict, folding)
    pieces = [
        f"{repr(key)}: {_repr1(obj[key], newlevel, maxlevel, folding)}" for key in keys[:unfold]
    ]
    if fold:
        key = keys[-1]
        pieces.append(f"... ({fold} items are folded)")
        pieces.append(f"{repr(key)}: {_repr1(obj[key], newlevel, maxlevel, folding)}")

    return _join_with_indent(pieces, level, maxlevel, "{", "}")


def _repr_attrs(obj: Any, level: int, maxlevel: int, folding: bool) -> str:
    """Customized repr method for object attributes.

    Arguments:
        obj: The object need to be transferred to repr string.
        level: The current repr level.
        maxlevel: The max repr level.
        folding: Whether fold the "repr" of the object.

    Returns:
        "repr" of the object.

    """
    # pylint: disable=protected-access
    if not obj._repr_attrs:
        return ""

    attributes = []
    for attribute in obj._repr_attrs:
        value = getattr(obj, attribute, ...)
        if value is not ...:
            attributes.append((attribute, value))

    if not attributes:
        return "()"

    if level <= 0:
        return "(...)"

    newlevel = level - 1
    pieces = (f"({key}): {_repr1(value, newlevel, maxlevel, folding)}" for key, value in attributes)

    return _join_with_indent(pieces, level, maxlevel, "(", ")")


def _repr_builtin_sequence(  # pylint: disable=too-many-arguments
    obj: Sequence[Any], level: int, maxlevel: int, folding: bool, left: str, right: str
) -> str:
    """Customized repr method for sequence.

    Arguments:
        obj: The object need to be transferred to repr string.
        level: The current repr level.
        maxlevel: The max repr level.
        folding: Whether fold the "repr" of the object.
        left: The left bracket symbol.
        right: The right bracket symbol.

    Returns:
        "repr" of the object.

    """
    if getattr(obj, "_repr_non_empty", False) and level <= 0:
        return f"{left}...{right}"

    object_length = len(obj)
    if object_length == 0:
        return f"{left}{right}"
    if level <= 0:
        return f"{left}...{right}"
    newlevel = level - 1

    fold, unfold = _calculate_fold_number(object_length, repr_config.maxlist, folding)
    pieces = [_repr1(item, newlevel, maxlevel, folding) for item in obj[:unfold]]
    if fold:
        pieces.append(f"... ({fold} items are folded)")
        pieces.append(_repr1(obj[-1], newlevel, maxlevel, folding))

    return _join_with_indent(pieces, level, maxlevel, left, right)


def _calculate_fold_number(length: int, max_length: int, folding: bool) -> Tuple[int, int]:
    """Calculate the number of the folded and unfolded items.

    Arguments:
        length: The object length.
        max_length: The configured max length.
        folding: Whether fold the "repr" of the object.

    Returns:
        The number of the folded items & the number of the unfolded items.

    """
    if folding and length > max_length:
        return length - max_length + 1, max_length - 2
    return 0, length


def _join_with_indent(
    pieces: Iterable[str], level: int, maxlevel: int, left: str, right: str
) -> str:
    """Handle the indent, newline and "," of the string list.

    Arguments:
        pieces: The string list need to be transferred to repr string.
        level: The current repr level.
        maxlevel: The max repr level.
        left: The left bracket symbol.
        right: The right bracket symbol.

    Returns:
        Repr string with indent, newline and ",".

    """
    # pylint: disable=protected-access
    inner_indent = repr_config._indent_str * (maxlevel - level + 1)
    outer_indent = repr_config._indent_str * (maxlevel - level)

    sep = f",\n{inner_indent}"
    return f"{left}\n{inner_indent}{sep.join(pieces)}\n{outer_indent}{right}"
